Anterior cruciate ligament (ACL) injuries and bone tunnel enlargement (BTE) after ACL reconstruction (ACLR) remain frequent issues. Bone dust (BD) produced by tunnel preparation with osteogenic ability and reverse drilling (RD), an easy compaction technique, make it accessible to enhance tendon-bone healing in ACLR. We hyposize that RD and BD synergistically improve outcomes after arthroscopic ACLR by improving peritunnel bone and preventing BTE.

Compaction technique can create a denser bone tunnel wall with more cancellous bone autografting in situ by sequentially compressing cancellous bone trabeculae to bone tunnel walls, in contrast to conventional extraction reaming by which an enlarged gap is created and initial direct integration is limited between implants and bone, as chunks of cancellous bone are torn out, thereby being removed outside the tunnel. Biologically, a compaction technique was reported to increase the bone volume around grafts and provide a larger area of bone-to-graft contact for bone integration because of the spring-back effect. Mechanically, compaction of the bone graft into the femoral tunnel was reported to significantly increase stiffness of the grafts. Reverse drilling (RD) can compress peritunnel bone at the time of bone tunnel preparation to make the tunnel wall denser and smoother in comparison with extraction drilling (ED), reverse drilling yields the same compaction effect as the compaction technique. Bone dust (BD) is commonly defined as pieces of bone produced by a power-driven tool. It is universally accepted that bone debris more than 200 mm in particle size is classified as particulate bone and that bone debris no more than 200 mm is classified as BD. When applied for ACLR, BD could fully utilize the advantages of an autologous bone graft while avoiding invasive and traumatic bone harvesting procedures, as bone tunnel preparation is accompanied by the production of a considerable amount of BD. Therefore, BD grafting is promising for improving tendon-bone healing with safety and simplification. We refer to the technique of retaining BD in the bone tunnel after RD as the reverse drilling technique. We hyposize that reverse drilling technique can improve outcomes after arthroscopic anterior cruciate ligament reconstruction by improving peritunnel bone and preventing bone tunnel enlargement.

Inclusion Criteria:

Patients with definite anterior cruciate ligament injuries on imaging or intraoperative arthroscopy (Sherman grading II and III), plan surgery within 45 days from injury; have basic literacy skills and unimpeded communication; have a smartphone and are able to use WeChat; and have been given informed consent and have signed to obtain an informed consent form, and the process must be in accordance with GCP requirements.

Exclusion Criteria:

1) Combined with other knee injuries (posterior cruciate ligament injury, patellar dislocation, osteoarthritis, etc.); 2) Suffering from systemic immune diseases; 3) Presence of other diseases or inflammatory diseases of the knee, including osteoarthritis, cervical spondylosis, rheumatoid arthritis, fibromyalgia, and rheumatic polymyalgia, etc.; 4) Patients who have had localized hormone injection therapy within 3 months; 5) Those who have participated in a clinical trials or are undergoing other clinical trials; 6) Those with severe primary cardiovascular lesions, pulmonary diseases, endocrine and metabolic diseases or serious diseases affecting their survival, such as tumors or AIDS, which in the opinion of the investigator are not suitable for enrollment; 7) Those with severe hepatic lesions, renal lesions, and hematologic lesions, such as renal function exceeding the upper limit of normal values and hepatic function exceeding two times the upper limit of normal values; and 8) Those with viral hepatitis, infectious diseases, severe abnormalities of coagulation mechanism and other diseases that the investigator considers inappropriate for surgery; 9) Pregnant or lactating women, or those who plan to conceive during the follow-up period, with a positive result of urinary human chorionic gonadotropin test prior to sampling; menstruating women should wait until the end of their menstruation period to undergo the surgery; 10) Patients with severe neurological or psychiatric disorders; 11) Those with a suspected or confirmed alcoholic substance abuse history; 12) Vulnerable groups: mentally ill, critically ill patients, pregnant women, illiterate, minors, cognitively impaired.

Surgical doctor team, patient, outcome assessor, data analyst and image reviewer are masked.